This invention relates to cell surface molecules and more specifically to T-cadherin, a new cell adhesion molecule of the cadherin family.
Cadherins are a family of transmembrane glycoproteins that mediate adhesive interactions in the developing and adult organism through a Ca2+-dependent mechanism (Takeichi, 1988 and 1990, review). It has been suggested that the cadherins arose from a common ancestral gene. Duplication of the gene may have resulted in the formation of a structurally related family of molecules with heterogeneous sequences. Cadherins share their overall structure which, at the extracellular region, is subdivided into a signal peptide, a prepeptide and five related extracellular domains and is followed by a transmembrane domain and a highly conserved stretch of cytoplasmic amino acids, that is suggested to provide a linkage with the cell's cytoskeletal network. The signal peptide and the prepeptide are readily cleaved and are absent from the mature protein. Several members of the cadherin family have been characterized. N-cadherin is found in the nervous system during development and has been shown to be a strong mediator of nerve fiber growth in vitro. In addition to neural tissue, N-cadherin is also expressed in heart and skeletal muscle and in lens cells. E-cadherin (also known as uvomorulin in the mouse) is a component of epithelial cells and P-cadherin is found in placenta.
T-cadherin, which is subject of this application, is a novel member to the cadherin family that shares the overall cadherin structure in the extracellular region, but lacks the conserved cytoplasmic sequences. Therefore, a new mode of T-cadherin function is proposed, in which T-cadherin regulates the adhesive cell properties not through a direct linkage with the cytoskeleton, but through higher membrane mobility and ready access to its extracellular ligand. The pattern of T-cadherin expression suggests a key role in the establishment of the pattern of nerve fiber growth in developing embryos. Furthermore, T-cadherin is the first molecularly characterized polypeptide to be identified in a segmental pattern as epithelial somites undergo the transition to form the dermamyotome and sclerotome. The expression in only one half of the somitic sclerotome, that eventually will give rise to vertebrae, suggests that T-cadherin plays a key role in the segmentation of vertebrate embryos. Segmentation is a crucial property of the vertebral column that allows flexibility and provides an individual with the ability to bend the back. T-cadherin has also been identified in muscle cells and blood vessels. In muscle, T-cadherin may be involved in cell differentiation and function. Expression in blood vessels may suggest that T-cadherin may be associated with the vascularization of tumors. A tumor remains small unless provided with blood capillaries. The control of vascularization that may be possible with the reagents described in this invention, may therefore be useful in controlling tumor formation and metastasis.
The identification of molecules which regulate and direct nerve fiber growth is important to the study of nerve regeneration. After being severed, neurons either degenerate or remain in a state of severe atrophy. The prognosis for recovery of these damaged neurons is very poor. Therefore, the use of molecules such as the T-cadherin cell adhesion molecules may influence neurons to regrow their axons and guide the axons to reinnervate their corresponding target cells. Eventually, this may lead to relief from the disabling effects of stroke or trauma to the nervous system.
There thus exists a need for the identification and characterization of cell surface adhesion molecules which may be involved in regulation of development in the embryo or recovery of traumatized neurons including methods of detecting and utilizing these molecules. The present invention satisfies this need and provides related advantages as well.